In recent years, silicon carbide (SiC) ceramics have been used in a variety of industrial fields including semiconductors, automobiles, chemical plants, and machine tools, due to their heat resistance, oxidation resistance, abrasion resistance, hardness, and other excellent properties. In order that silicon carbide find further widespread commercial applications, not only its manufacture, but also the bonding of silicon carbide ceramics pieces to each other or to metal pieces are thought key. A simple economical bonding technique is desired particularly from the industrial standpoint.
The prior art well-known ceramics bonding methods typically include (1) mechanical bonding, (2) brazing or metallizing, (3) solid phase or fusion bonding using metal foils or bands, and (4) bonding utilizing chemical reactions. The first three of these bonding methods are not regarded as simple or inexpensive, because mechanical bonding (1) requires a high precision of operation, and metallizing (2) and solid phase or fusion bonding (3) require special equipment.
Bonding method (4), which utilizes chemical reactions, is most simple. Bonding of silicon carbide utilizing a chemical reaction, more particularly, bonding of reactively sintered silicon carbide is reported by Izeki et al, Yougyou Kyoukai Si) Journal of Japanese Ceramic Society), Vol. 91, 259-264 (1983) Izeki's bonding method involves: applying a bonding composition of silicon carbide powder, carbon powder, and a binder (a mixture of phenol resin and furan resin in a solvent) to a surface of a first ceramic piece to be bonded; joining the first piece to a second piece; pressing the assembly under pressure; and introducing silicon to the bonding interface in vacuum at 1450.degree. C., to give bonding.
This method, however, has a problem in that expansion occurs due to a reaction between the introduced silicon and the carbon in the bonding composition, so that silicon is further introduced into the voids created by the expansion, to form a layer consisting solely of silicon, which layer may become a cause of breakage. To avoid the above expansion, pieces to be bonded together need to be held in close contact during heat bonding. The holding of pieces together in intimate contact under such elevated temperatures requires an advanced level of technology, and often imposes limitations on the manufacturers of bonding equipment. This often invites a situation where only the manufacturer of ceramic pieces can carry out the bonding of ceramic pieces.
A further difficulty arises in bonding of complex shaped pieces. In order to produce an article of complex configuration by reactive sintering, it has generally been adopted to bond pieces, while they are in a calcined state, with a bonding agent having the same composition as the calcined pieces before reactive sintering is carried out. This method has disadvantages in that resulting bond strength is low and such bonding can only be practiced by ceramics manufacturers.